Applicant claims priority under 35 U.S.C. xc2xa7119 of German Application No. 102 04 384.1 filed Feb. 4, 2002.
1. Field of the Invention
The present invention relates to a method for controlling stationary fire-extinguishing systems, and in particular for controlling fire-extinguishing installations that are operated with liquid or gaseous fire-extinguishing agents. In addition to the fire-extinguishing devices which dispense liquid or gaseous fire-extinguishing agents, the important components of stationary fire-extinguishing systems are the fire alarm devices for controlling fire-extinguishing installations. Such fire-alarm devices are in the center of the present invention.
2. The Prior Art
Fire-extinguishing systems include a reservoir of fire-extinguishing liquid or gaseous agents that is connected with a monitored area (building, warehouse, etc.) via a more or less branched system of pipelines. In the event of a fire, the extinguishing agents are released by means of fire-extinguishing nozzles. The nozzles are arranged in accordance with the specific fire-extinguishing task on hand.
Depending on the type of fire hazard involved and the areas that have to be protected, widely branched sprinkler systems or fine-spray fire extinguishing systems are employed that produce a highly effective water mist. Also gas fire-extinguishing systems may be used which operate with an inert gas such as carbon dioxide as the fire-extinguishing agent.
To fight a fire effectively, the point or points at which the various types of fire-extinguishing systems are triggered plays a special role.
This task is assumed by fire-alarm systems that, in most cases, are equipped with detectors for an early detection of various fire identification characteristics.
Such fire-alarm systems include one or more detectors that are accommodated in fire-alarm devices. The devices are often connected with a fire-alarm center via signal lines (fire alarm lines).
Fire-alarm installations are in most cases built from a great number of sturdy fire-alarm devices.
The detectors react to the occurrence or change in measurable fire identification characteristics such as the temperature, the radiation, particulate matter (aerosols), or gases characterizing a fire.
In the fire alarm center, the measurement signals received from the fire-alarm devices installed in the monitored areas of the fire-extinguishing system are processed, and, in the event of an alarm, corresponding control commands are transmitted to the fire-extinguishing system.
All physical or chemical changes of condition parameters occurring in the area monitored by a fire-alarm system that are caused by a fire and can be detected by means of sensor elements or detectors are summarized herein under the term xe2x80x9cfire identification characteristicsxe2x80x9d.
Thus the fire identification characteristics are condition parameters of the fire. These parameters include, for example, the ambient temperature, the composition of the gas (smoldering or combustion gases), the density of optically detectable smoke or soot particles (aerosols), and the electromagnetic radiation emitted by fires on different wavelengths.
Stationary fire-extinguishing systems are successfully employed for fire-fighting purposes in many areas of fire protection in buildings, equipment installations, or in the area of warehousing of materials.
It is known that the fire-extinguishing process is triggered and the fire-extinguishing agents are released by automatically operating fire-alarm devices.
So that the start of a fire can be detected early, the fire-alarm devices should be installed as closely as possible to a site where a fire may possibly originate, on the one hand. On the other hand, however, the local circumstances have to be taken into account as well.
In this connection, in addition to the early detection of fires, the prevention of false fire alarms as well is the focus of the further development of fire-alarm devices.
False fire alarms are frequently triggered by uncritical parameters or processing process-conditioned sources. A rise in the temperature within the vicinity of a heat-alarm device that cannot be attributed to the start of a fire may lead to a false alarm as well.
With many conventional fire-extinguishing systems, the entire supply of fire-extinguishing agents is often consumed without interruption after a fire alarm has been triggered and the extinguishing process has been activated.
However, such extensive fire-extinguishing measures are normally not required in connection with smaller, locally confined fires.
False alarms cause even greater damage: not only will the consumed supplies of fire-extinguishing agent (CO2-gas), which are available only to a limited extent in connection with certain fire-extinguishing systems, need to be replaced at high cost and with great expenditure of time, but also the fire-extinguishing agents unnecessarily dispensed may cause damage to persons and equipment, or may shut down entire manufacturing areas.
Numerous proposals have been made for resolving these known problems associated with the operation of stationary fire-extinguishing installations.
DE 100 12 705 A1 discloses a method and a device for the early detection and fighting of fire in indoor and outdoor areas, in particular in the area of residential houses and of buildings. The system includes a fire-extinguishing device and a fire alarm system that has one or more fire alarm devices with at least one detector. The detectors detect the same or different fire identification characteristics and trigger a fire-alarm signal after one or more pre-adjustable alarm thresholds of the detected fire identification characteristics have been exceeded. This fire-alarm signal then activates the fire-extinguishing system.
A method and a system for detecting fire in a monitored room (or space) with the possibility of increasing the sensitivity of the detector system are known from DE 41 42 419 A1. An undefined number of detectors are switched with respect to their sensitivity, and the number of detectors to be switched over is adapted to the further development of the fire.
A method for automatically reporting and extinguishing fires is known from DE 23 44 908 C2. In this process, the fire-extinguishing system is controlled and actuated only after a flame report is available. This report has to be preceded by two smoke reports and one heat report. The continuing presence of flames has to be tested in this connection at defined time intervals by a flame-reporting alarm device, and the dispensation of the fire-extinguishing agent either has to be maintained or shut down. However, it is not stated how exactly this testing procedure is carried out. The aim of this known method is to prevent false alarms and damage caused by any unnecessary influence of fire-extinguishing agent.
A similar fire-extinguishing method is described in DE 196 27 353 C1. In this method, the development of the fire is detected by sensors distributed over the room and the fire-extinguishing agent is dispensed in a manner adapted according to the development of the fire in terms of space.
DE 199 52 327 A1 discloses a fire sensor and a method for detecting a fire as well. The smoke signal emitted by the fire sensor is additionally corrected by correlating actual outside temperature and the rate at which the temperature is rising.
The purpose of such a correction is to adapt the smoke detection sensitivity of the sensor to the ambient temperature and the rate at which the ambient temperature is changing.
The probability of a false alarm is expected to be reduced by this method, and early triggering of the alarm is said to be achievable at the same time.
However, this patent document relates to the detection of fires only up to the activation of the fire-extinguishing system and contains no reference to the fire-extinguishing process and the control of the fire-extinguishing system after the alarm has been triggered.
The known fire-extinguishing systems have the drawback that they fail to take into account the physical and chemical changes caused by a fire and the extinction process that starts within the environment of the fire alarm device, such as a strong development of smoke, soot particles, temperature changes caused by the influence of the fire-extinguishing agent or water mists, as well as changes occurring in the composition of the gas etc. Without taking into account these changes within the area of a fire, conventional fire alarm devices cannot supply any adequately exact picture of the actual fire event and are only conditionally suited for controlling the fire-extinguishing process.
Therefore, the object of the present invention is to develop a method for controlling stationary fire-extinguishing systems, and to specify how such systems are operated, that eliminates the aforementioned drawbacks.
The method of the invention generates measurement signals that can be easily evaluated, are suitable for controlling the fire-extinguishing system despite changes occurring in the environmental conditions in the event of a fire, and can be used for effectively controlling the fire-extinguishing process.
In accordance with the invention, a method is provided in which after the preset alarm thresholds of one or more fire identification characteristics have been exceeded and the fire-extinguishing device has been activated, at least one of the detectors detecting the fire identification characteristics is switched to a higher degree of sensitivity. The selection of the detector or detectors to be switched to a higher sensitivity is adapted to the further development of the fire in terms of space and time. Additional advantageous implementations of the invention are discussed below.
In accordance with the fire-extinguishing method as defined by the invention, after a fire has first been safely detected, the detectors of the fire alarm devices are switched to a raised stage of sensitivity by exceeding one or more preset alarm thresholds. In this way, the development of the fire may continue to be effectively detected despite the development of smoke, the formation of vapors caused by evaporating fire-extinguishing agents, or other interfering influences.
Furthermore, the invention relates to a fire alarm device as defined by the invention for carrying out the method of the invention.
The method can be applied in a particularly advantageous manner with the use of infrared detectors serving as sensitive flame detectors.
The heat radiation occurring in fires can still be safely detected by raising the sensitivity of an infrared detector according to the invention even if the permeability of its ambient air has been reduced due to the fire. Furthermore, a local selection of the detectors to be changed to a higher degree of sensitivity may be carried out after the fire has been progressing.
A lesser degree of sensitivity is required in areas with less development of smoke, or where the detector is installed with only little spacing from the source of the fire, than in areas where the development of smoke is strong or the detector is installed far from the source of the fire.
The control is effected via the behavior of the fire identification characteristics in terms of time.
In an advantageous further embodiment, the switch-over processes (signal evaluation of the detectors) for increasing the sensitivity of the detectors may be adjusted with a selectable time delay after the start of a fire has been detected.
This flexible adjustment possibility allows one to take into account the development of a fire to be expected. The system may be tailored with the degree of endangerment to the objects to be protected, of which the fundamental characteristics are known.
The individual change-over processes for switching the detectors to a higher stage of sensitivity are effected by a control unit arranged in the fire alarm devices, or initiated by the fire alarm center.
The measured data of the actual local fire development transmitted by the detectors are used for this purpose.
The increase of sensitivity may be accomplished in steps, i.e. incrementally, or it may be a stepless, continuous increase.
The local or spatial selection of the detectors to be switched to a raised sensitivity, is carried out following the evaluation and taking into account the measured data transmitted to the fire alarm center.
The fire-alarm devices may be installed in different locations and aligned in a manner corresponding with the structure of the expected fire hazard potential. In this way, the development of a fire can be continually analyzed in the course of the extinguishing process from a number of directions.
In another advantageous embodiment, a detector element may be additionally arranged in one or more fire-alarm devices for controlling the continuing application of the fire-extinguishing agent.
An application of the fire-extinguishing agent that is adequate for fighting a fire is detected by this additional detector element and generates an extinction stop-signal for shutting the fire-extinguishing system down.
Another advantageous implementation of the invention is connected with the known method of applying the fire-extinguishing agent in a cyclic manner, with controlled dispensing of the extinguishing agent.
Since the sensitivity of the detector is adapted to trailing the fire event according to the invention, an exact reproduction of the actual development of the fire is produced that corresponds with the actually measured data.
If the analysis of the data measured by the detectors indicates that the fire will continue, an elapsed extinction cycle of the fire-extinguishing system is restarted.
If fire is no longer detected despite the higher sensitivity of the fire-alarm devices, the generation (triggering) of the activation signals is discontinued as well and the extinction process is terminated.
To assure a more far-reaching safety for completely extinguishing a fire, an after-extinguishing cyclexe2x80x94the extent of which can be presetxe2x80x94may be triggered after an extinction stop-signal has been generated by the fire-alarm system.
The parameter adjustments for the after-extinguishing cycle, depend in this connection on the degree to which the objects to be protected are endangered. These parameter adjustments include the duration of the extinction process and the amount of extinguishing agent.